Preparation of methane phosphonyl dichloride via phosgenation



United States Patent 3,179,696 PREPARATION OF METHANE PHOSPHONYL Di- CHLORIDE VIA PHOSGENATION Bernard B. Brown, Leland J. Lutz, and Charles J. Smith, In, Grand Island, N.Y., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Filed Jan. 15, 1954, er. No. 404,372 1 Claim. (Cl. 268-543) Our invention relates to a method for the preparation of certain dichloro compounds by phosgenation.

More particularly, our invention concerns a method in which the following reaction takes place:

R, R and R" being alkyl radicals.

To the best of our knowledge, the aforementioned reaction has not heretofore been carried out at least on a satisfactory basis, and the carrying out of the reaction to produce the desired compounds at a rapid rate and in good yield based upon the amounts of reactants taken is difiicult of attainment. One of these reasons is the tendency of the ester used as a starting material to chlorinate insufiiciently with the formation of monochloro compounds of the formula:

This is undesirable in that it represents reactant loss. Other reasons why it is difficult to carry out the desired reaction rapidly and in good yield are found in the tendency of the aforementioned monochloro compounds to condense with themselves and also to react with the ester starting material to form an anhydr-ide as shown in the following equation: (RO)(Cl) P(O)R"+(RO) (:RO)P(O )R"- In accordance with our present invention, we have discovered that by the use of certain critical reaction conditions, particularly relative amounts of reactants, temperature and pressure, it is possible to convert in high yield and at a rapid rate a phosphonate of the formula:

to a compound of the formula:

by reaction with phosgene, where R, R and R" are alkyl radicals. Thus, in accordance with our invention we react the phosphonate of the formula:

with from 2 to 3 molar amounts of phosgene at 100- 200" C. and at a pressure of 100-600 p.s.i.g., thereby rapidly producing a high yield of the desired product with minimum formation of by-products.

The following example illustrates the preparation of methane phosphonyl dichloride by the phosgenation of cliisopropyl methane phosphonate in accordance with the method which we have devised:

Pure diisopropyl methane phosphonate (11, of 1.4079) in the amount of one mole was reacted with 2.5 moles of liquid phosgene at a temperature of 100-120 C. and at a pressure of 350 p.s.i.g. fora period of 28 minutes. The reaction mixture was thereafter distilled at an absolute pressure of 1-2 mm. of mercury to yield a water-white liquid distillate which solidified rapidly to a colorless solid melting slightly above room temperature. The yield of the desired product, methane phosphonyl dichloride, was 48.5 percent. in two determinations, the product analyzed 52.47 and 52.67 percent hydrolyzable chlorine, the theoretical percentage for methane phosphonyl dichloride be ing 53.4 percent.

A similar experiment using the same proportions and pressure was run at a temperature of -95 C. Distillation at an absolute pressure of 12 mm. of mercury gave a colorless liquid product which on cooling precipitated only a very small amount of solid similar to that described in the preceding paragraph. Thus, the carrying out of the reaction at temperatures of 90-95 C. is undesirable.

Various modifications can be made in the specific procedures just described to provide other embodiments which fall within the broad scope of our invention. Thus, our invention is generally applicable in the preparation of compounds of the formula:

by reacting compounds of the formula:

with phosgene under the conditions specified. In the two preceding formulas, R, R and R" are alkyl radicals, the sum of the carbon atoms in R and R preferably not exceeding 8 and the number of carbon atoms in R" preferably not exceeding 4. Thus, R and R can be, or example, methyl, ethyl, n-propyl, n-butyl, Z-ethylhexyl and the like and R" can be, for example, methyl, ethyl, n-propyl, i-propyl, n-bu-tyl, and isobutyl.

We claim:

A method for the preparation of a compound of the generic formula:

which comprises reacting a compound of the formula:

(R n m 0) (R") with from 2.0 to 3.0 molar amounts of phosgene at a temperature within the range of IOU-200 C. and a pressure within the range of -600 p.s.i.g., R and R being isopropyl radicals and R" being a methyl radical.

References Cited by the Examiner UNITED STATES PATENTS 8/58 Dawson et al. 260--543 3/60 Dawson et al. 260-543 

